The present invention relates to a self-propelled cleaning device and to a method of operation thereof.
An example of a self-propelled cleaning device has been disclosed in Japanese Application Patent Laid-Open Publication No. Hei 08-215116. In the cleaning device described in this publication, the state of the wall in front of the cleaning device body is checked at each forward stop position. A determination is made as to whether or not there is a continuous flat surface in front of the body; and, in the case where there is a flat surface, the body is moved so as to be at right angles with respect to the flat surface, and the zero point for the orientation sensor is set.
Another example of a self-propelled cleaning device is disclosed in Japanese Application Patent Laid-Open Publication No. 2002-204768. The cleaning device disclosed in this publication comprises a propelling means for moving the body; a moving direction changing means for changing the direction in which the body moves; and a movement controlling means for controlling the movement of the body. The movement controlling means causes the cleaning device body to zigzag within a region defined by a pair of straight lines. When the cleaning device body cannot spiral any further forward, the advancing direction of the body is changed so as to be directed away from the regional line obstructing the spiral advance. It is to be noted that this cleaning device body comprises an obstacle detection means for detecting an obstacle positioned in the advancing direction of the cleaning device body; and, when an obstacle is detected, the advancing direction of the cleaning device is changed to a direction that avoids the obstacle.
In the above-mentioned cleaning device disclosed in Japanese Application Patent Laid-Open Publication No. Hei 08-215116, a wall in front of the body is detected, the body is positioned at right angles to the wall and the zero point for the orientation sensor is set. However, with this method, while the direction can be detected when the wall is a substantially flat surface, when the wall is uneven, it may not be possible for the angle of the wall to be accurately detected. In addition, when obstacles, such as chairs or desks, are within the region to be cleaned, the path of movement must be changed in order to avoid such obstacles, but sufficient consideration is not given to the disclosed in this method.
Meanwhile, in the self-propelled cleaning device disclosed in Japanese Application Patent Laid-Open Publication No. 2002-204768 mentioned above, when obstacles are detected, the direction of movement is changed to avoid the obstacles. However, in this type of simple system for avoiding an obstacle, even when small obstacles are encountered, there is a great change in the path of movement, and this causes large regions to be left uncleaned. As a result, there are regions that are not cleaned, and thus there is the possibility that it may become necessary to clean the uncleaned regions again, resulting in a low cleaning efficiency.